Telegraph signaling apparatus



Sept. 5, 1933. H. v. HIGGITT TELEGRAPH SIGNALING APPARATUS 3 Sheets-Sheet 1 Filed Jun 20. 1932 III l O 11''! II D I II II \lllllll Ill Ill |||||||||l III all .1

ATTORNEXQ Sept. 5, 1933. v HlGGlTT 1,925,756

TELEGRAPH SIGNALING APPARATUS Filed June 20. 1932 s Sheets-Sheet 2 T TURNE XS',

3 Sheets-Sheet 3 1Il1 1 H'HH 111111 /N VENTO R ATTORNEXf.

H. V. HIGGITT TELEGRAPH SIGNALING APPARATUS Filed, June- 20. 1932 Sept. 5, 11933.

1 4 B A13 A BWIAIBIA 1 1 Flg 111 111 111 11 1 11 '71 1 18 BAIB 11 U 1 1 I11 ABiA Patented Sept. 5, 1933 rriiar Fri-I TELEGRAPH SIGNALENG APPARATUS Harry Vernon Higgitt, London, England, assignor to imperial and International Communications Limited, London, England, a British company Application June 20, 1932, Serial No. 618,360, and

in Great Britain July 8, 1931 10 Claims;

This invention relates to telegraph signaling apparatus, and particularly to telegraph systems for signaling by means of theMorse code in which the signals consist of electrical conditions which are made to persist for various time intervals and which have been termed double current cable code signals. An example of such signaling is set forth in the specification of British Patent No. 294,715 granted to Harry Vernon Higgitt and Eastern Telegraph Company Limited,

dated May 5, 1927, and the preferred method consisted in representing a dot by a marking current having a duration of 100 per cent of a signaling interval, while a dash was represented by a spacing current having the same duration and a space by a marking current lasting for per cent of a signaling interval. followed by a second 50 per cent of spacingcurrent. The current conditions need not consist of marking and spacing currents, that is 20 to say, of currents of opposite sign, but other of electrical conditions may be employed double current signaling. Thus, for example, wireless signaling, one condition may consist the transmission of radio impulses, and the r condition the failure to transmitiany imices; or again one electrical condition may consist in transmitting a carrier wave modulated at one frequency and the other condition of a m carrier wave either unmodulated or modulated at another frequency.

The pro ent invention aims at enabling double ent cable code signals as referred to above, ti ansmitted by a wireless transmitter or a wired telegraph transmitter, to be allocated to two or more channels in a predetermined order. This well known that ordinary cable code signals may be divided between two or more channels, but the special form of cable code signals referred to as double current cable code signals necessitate the i) provision of special devices for dealing with channels. The channelling of a telegraph circuit has several advantages; one advantage consists in the fact that with high speed working the speeds of the individual channels can be kept low and within the capabilities of one operator at each station, 'le another advantage lies in the fact that in a wireless circuit periods when th working conditions are poor the same messages can be sent over two or more channels one slightly later than the other so that at the receiving station the can he read more accurately. According to the present invention, a telegraph r.' 'naling apparatus for signaling by means of the viorse code in which the signals consist of elec- 'rical conditions which are caused to persist for (c1. rzsss various time intervals, is provided with switching gear for allocating signals to two or more channels in a predetermined sequence. The switchinggear may be of any kind which allows circuitsto be closed for predetermined time intervals and enables the time of closing and opening the ci'cuits to be related in a definite timed and phased relationship. The switches may in particular be of the type in which spring contacts are closed by operating cams, or of the rotary distributor type with crushes bearing on contact segments. A transmitter and when necessary," a transmitting relay is provided for each channel, together with a number of switches or one compound switch capable of performing all the necessary functions, automatically driven. In the case of cam operated switches, conveniently one switch deals with the dot signaling levers of the transmitters and a second switch with the dash signaling levers, each then having the same numher of effective contacts as there are channels. rinally, the current impulses-to the split windings of the line relay or the current impulses passing to the line from the split battery, pass through the contacts of a reversing switch operated at the aggregate speed of the signals passing to line.

When a rotary distributor switch is employed, alternative segments of the distributor are connected to the dash and dot levers respectively of the transmitters of the difierent channels.

In order that the invention may be clearly understood and readily carried into effect, it will nowloe more fully described inconnection with certain examples which will be set forth with reference to the accompanying drawings. The example of the signaling system illustrated is that in which there are two or more channels for the cable code signals as set forth in the specifications of British Patents Nos. 267,180 dated Oct. i4, 192?, and 294,715, dated May 5, 1927, both granted to Harry Vernon I-Iiggitt and Eastern Telegraph Company Limited which consist of 190 per cent marking or positive current for a dot, per cent spacing or negative current for a dash and 50 percent marking current followed by 50 per cent spacing current for a space in themanner already referred to.

In the drawings Figures 1 to 8 are diagrams illustrating specimens of signals which as there illustrated are to be allocated to two channels.

Figure 9 is a circuit diagram showing the send ing connections .in the case of two channels when cam-operated switches driven by phonic motors are employed.

Figure 10 is a similar diagram of connections showing a system in which a line relay with split windings is employed instead of the split battery shown in Figure 9.

Figures 11 to 17 are diagrams showing the timing or phasing of the sending mechanism illustrated in Figures 9 and 10.

Figure 18 is a diagram of connections of a system for allocating the double current cable code signals to three different channels and in which the switching gear is in the form of a rotary distributor.

Referring first of all to Figures 1 to 8, in Figure 1 :1 indicates the current impulses employed as the spacing signal. It can be seen that this consists of an impulse of marking or positive current for the first half of a signal interval for one channel followed by an impulse of spacing or negative current for the second half of the interval.

The signal employed as a dot is shown at b and'consists of marking or positive current lasting for 100 per cent of the signal interval. The

I dash signal is shown ate and consists of 100 per cent of spacing or negative current.

Figure 2 shows a succession of spacing signals sent alternately on the two channels which are indicated as A and B in all the figures from Figures 2 to 8. The spacing signals can be easily picked out in the successive channels in Figure 2.

Figure 3 illustrates the current impulses used on this signaling system when spacing signals are sent continuously on channel A and interposed between them are continuous dots on channel B.

In Figure 4 continuous spaces are also being sent on channel A and interposed between them to form channel B is a continuous series of dashes. In Figure 5 the first half of the diagram shows continuous-dots being sent on both channels and the second half of the diagram shows continuous dashes being sent on the channels A and B. In Figure 6 on channel A the signal being sent is the letter A which in the Morse code is represented by dot-dash whileon the channel B continuous spaces are being sent. If Figure 6 is examined carefully it will be seen that in channel A the signal represented is dot, dash, space, dot, dash.

In Figure '7 spacing signals are shown as sent continuously on channel A and on channel B letters D are sent which are represented in the Morse code as dash-dot-dot. If Figure 7 is examined the signal impulses on the B channel are dash, dot, dot, space.

Finally, for the purposes of illustration, Figure 8 is illustrating letters A sent on the A chan nel and letters D on the B channel. Thus, if the current impulses are examined, the sequence on the A channel is dot-dash-space-dot-dashspace which represents letter A followed by a' space followed by another letter A. Similarly, the impulses on the B channel consist'of dashdot-dot-space-dash-dot. This is, of course, a letter D followed by a space and the first part of a second letter D. The above illustrates clearly the kind of current impulses which have to be sent to line when signaling with the double current cable code and sending signals of two channels on the same line.

Oneform of the circuit connections of the sending arrangements is illustrated in Figure 9.

As two channels are provided, the sending ar rangements include two automatic cable code transmitters driven at equal speeds. In Figure 9,

the transmitters are indicated generally at TA and TB; they may conveniently be driven by phonic motors and they are adjusted to produce block signals, that is to say, signals with no spacing between consecutive dots and dashes. The timing of the two transmitters is such that they are half a channel signal out of step. This is indicated by the arrows l, 2 which also serve to indicate the beginning and end of current inipulses in the transmitter coils 3, 4, 5, 6. As shown in Figure 9, the energization of one of these coils draws down the corresponding sounder contact levers '7, 8, 9, is from their back contact butts ll,

'12, 13, i l on to the corresponding front contacts l5, 16, 17, 18. On the A channel the contact lever 7 is the dot lever and the contact lever 3 is the dash lever, while on the B channel the lever 9 is the dot lever and the lever 10 the dash lever. Ifa dot is sent on the A channel followed by a dot on the B channel, the winding 3 will be ener gized and the lever 7 drawn down on to the contact for the whole of a channel signal. El'alfway through that time, however, the coil 5 is energized and pulls down the lever 9 on to the contact for a whole channel signal. This, however, will be elaborated below in connection with further figures of the drawings.

It will be noticed that the front contact butts 15 and 1'? of the dot signaling levers Z 2: of both transmitters are connected through a re sistance TA to the positive pole of the split battery SE to which are also connected the back contact butts l2 and 14 of the two dash signaling levers 8 and 10. On the other hand, the two back contact butts 11 and 13 of the dot signaling fr levers '7 and 9 and the two front contact butts l5 and 18 of the dash signaling levers 8 and 10 are all connected through the resistance TB to the negative pole of the split battery SB.

As already mentioned there are a pair of auto matic switches which are in reality combining switches, one shown at 19 being allocated to dots and the other shown at 20 allocated to da These switches are closed, in the example by cams for definite periods, which cams are driven by a phonic motor. In tl: case two channels as shown in Figure 9, each the switches 19 and so has two contact levers 21, 22 and 23, 24.. The dot signaling levers 5, 9 of t two transmitters are connected to the centac 25 and 26 of the dot combining switch and also the dash signaling levers 8 and 10 of the two transmitters are'connected to the two contacts 27, 28 of the dash combining switch 20. cams operating the levers 21 and 22 are dcgrees out of phase so as to close these contact arms over opposite halves of each revolution as indicated by the arrows 29, 30. The two levers 23, 24 of the dash combining switch 2% are also closed 180 degrees out of phase with each other, but each .1 V

90 degrees out of phase with respect to levers 21, 22 of the dot combining switch is; this is indicated diagrarnatically by the arrows 31,

Connections are made between the contact levers 21, 22 23, 24 of the two coinbin switches 19 and 26 and the contacts of third or reversing switch 35. The levers 37 of this switch are closed by cams driven he phonic. motor, but at twice the speed of the switches 19 and20 because there are two channels to be dealt with. In general terms, the switch 35 is driven at the aggregate speed of he passing to line. The two contact levers 21, 22 of the dot combining switch it are connected directly to the contact 33 of the switch 35, and

similarly, the two contact levers 23, 24 of the dash combining switch 20 are connected to the contact 34 of the reversing switch35. The timing of the periods of closing of the contact levers of the reversing switch 35 are as follows:The lever 36 makes contact during the middle portions of the periods when the dot combining switch 19 makes contact, whereas the other lever 37 makes contact in the intervening parts of a revolution of its operating cam. This timing is indicated diagramatically by the arrows 38 and 39. The contact levers 36, 37 of the reversing switch 35 are connected directly to line L, while the mid-point of the split battery SB is connected to earth at E.

A slight variation is shown in Figure 10 where the levers 36, 37 of the switch 35 are connected through a battery RB to the junction of the split windings l0, l1 of the line relay LR. The corn tact lever 42 of this relay is connected directly to line L and connects positive or negative of the split battery SB to line, depending upon which of the coils 40, ll attracts the contact arm 42. Again the mid-point of the split battery SB is earthed at E.

In Figure 9 also jack contacts are provided for taking a record of the signal impulses sent to line. The record contacts 43, 44 for the A channel are closed by a camdriven from the phonic motor for a short period at the middle of a signaling period on the A channel as indicated by the arrow 45. Similarly, the contacts 46, 47 for the record of the B channel are closed for short times at the middle of signal periods on the B channel as indicated by the arrow 18.

In order to make still more clear the method of operation of the timing of the switches in the sending connections shown in Figures 9 and 10, the effect produced by the switches in sending a simple signal is illustrated diagrammatically in Figures 11 to 17. Figure 11 indicates the sending on the A channel of two spaces from the point 49- to the point 50 followed by a dot from D to 51, a dash from 51 to 52 followed by spaces from 52 to the end of the figure.

Figure 12 shows a signal sent on the B channel whichfrom 53 to 54 consists of two spaces, from 54-to 55 consists of one dash with three dots from 55 to 56 followed by spaces. These re the signals appearing at the levers '7, 8, 9 and of the sounders of the two channel transmitters TA and TB in Figure 9. It will be realized that during the space signals, no current fiows in any of the windings 3, 4, 5 and 6 so that all four of the contact levers 7, 8, 9, 10 reon their back contacts 11, 12, 13, 14; When a dot is sent on. channel A as at 50 to '51, the coil is energized, drawing lever ion to contact and that persists for a whole channel signal period indicated by the arrow 1 in Figure 9 and indicated by the period from 50 to 51 in Figure 11. Similarly, the dash from 51 to 52 means that the dash lever 8 of the A channel is drawn on to its front contact 16 for a complete channel signal period. Figure 11 shows that block signals are produced at the sounder contacts as there is no space between the dot 50, 51 and the dash 51,. 52. Similarly, in Figure 12 the dash between 5-1 and 55 means that the dash signaling lever 19 of the '5 channel is drawn on to its front contact 13 fora whole channel signal period. It is also instructive to notice that tliis dash in Figure 12 starts at an instant half way between 53 and 51 in Figure 11 showing that the two transmitters are 186 degrees out of phase as already mentioned and as indicated by the arrows 1 and 2 in Figure 9. The three dots be tween 55 and 56 mean that the dot signaling lever 9 of the B channel is drawn down on to its front contact 17 for three complete channel signals.

Figure 13 shows the time periodswhen the contact levers of the combining switches 19 and close. It will be seen that this figure is only another method of representing the condition shown by the arrows 29, 30, 31 and 32 in Fig ure 9. The top row in Figure 13 marked 21a shows the time periods when the lever 21 of the dot combining switch 19 is closed. The second row marked 22a similarly indicates the time periods when the lever 22 of the dot combining switch 19 is closed. Again the third line marked 23a shows the time periods'when the lever 23 of the dash combining switch 20 is closed, while finally, the last line 24a indicates the time periods when the lever 24 of the dash combining switch 20 is closed. I

In a similar fashion Figure 1 1 shows the periods during which the contact levers 36, 37 of the reversing switch are closed. t will be noticed that a channel signaling period such as that elapsing between the points and 51 in Figure 11 is cut up into the four periods 57, 58, 59 and 60 in Figure 14 corresponding respectively with the arrows 38 and 39 in Figure 9. The upper row in Figure 14 marked 35a therefore gives the time intervals when the lever 35 of the switch 35 makes contact and the lower 7 row 37a indicates the time periods when the lever 37 of the switch 35 makes contact.

Figure 15 shows the resulting double current channel signals sent to line L by the switching arrangement. It will be seen that the second half of a dot signal as sent to line, that is, the part which distinguishes it from a space signal,

as for example the second half of the signal between 61 and 62, is taken from the third quarter of the dot signal formed by the dot lever 7 or 9, which in the example taken is the third quarter of the signal between 50 and 51 in Figure 11. On the other hand, the first half of a dash signal as sent to line, that is, the part which distinguishes it from a space signal as, for example, the first half of the signal between 62 and 85 is taken from the second quarter of the dash signal formed by the dash lever 8 or 10 which, in the example taken is the second quarter of "the signal between 54 and 55 in Figure 12. In other words, the line relay LR in Figure 10 is controlled in sequence by the signaling levers of the transmitters in the following order:- Dash lever 8 of A channeL dot lever 7 of A channel, dash lever 10 of B channel and dot lever 9 of B channel, and then the action is repeated in the same order. The result is that during the first half Z of an aggregate signal the line relay LR is controlled by a dash lever and the second half of the signal by a dot lever. In order to explain the spacing signals shown at the beginning and end of Figure 15, it may be noted that if no dash has been transmitted and the dash lever 8 or 1%) is on its back contact 12 or 14, marking or positive current is sent to line. In the case of the A channel, the circuit being in Figure 9 from the positive pole of the battery SB through contact 12, lever 8, contact 27, lever 23, contact 34, lever 37 to the line L. The reverse is the case with the dot levers of the transmitters, and therefore, when all'the four levers 7, 8, 9, 10 are on their back contacts, marking and spacing currents are sent to line alternately, each for 50 per cent of a signaling period as shown between 63 and 61 and between 64 and 65 in Figure 15, with the result that space signals of the double current cable code already described are transmitted.

Figure 16 shows the time periods when the record contacts 43, 4e and 46, 47 are closed and correspond to the arrows 45 and a8. As contact is made for a short time only at the middle of a channel signal, it will be seen that in the case of a space transmitted, contact is made round about the time when the line current is changing quickly from marking to spacing and consequently the recorder instrument gets only just a perceptible record as shown at 66 in Figure 17. In this figure the upper line 67 is a record of the signals in the A channel and the lower line 68 a record of the signals in the B channel. -v'hen a dot is being transmitted the recorder contacts take off a positive current sufficient to give a record indication of the kind shown at 69 in the A channel, or 70 in the B channel. Similarly, in the case of a dash, a negative or spacing current is taken off suflicient to give an indication of negative current as shown at 71 in the A channel or 72 in the 13 channel.

The switches such as 19 and 29 in Figure 9 for combining the signals of more than one channel may take the form oi a rotary switch or a distributor having contact seg ,nts with which brushes make contact. A. circuit diagram for such an arrangement is shown in Figure 18 in which there are three channels and three transmitters TA, TB, TC. The sounder contacts are as shown in Figure 9, the dot levers being shown at 7, 9 and 73, while the dash levers are shown at 8, 10 and 74;. The back contacts 11, 12, 13, 1e, 75, 76 with the front contacts 15, 16, 17, 18, 77, 78 are arranged in the same way and crossconnectod as in Figure 9, the split battery being shown at in Figure 18 earthed at E at its central point. I

The dot contact lever 7, 9 and 73 are connected to segments D 13*, D of the distributor switch,

while the dash contact levers 3, l0 and 7d are a connected to the contacts 13 D D of the distributor switch. The slip ring 79 of the switch is connected to the line L and the brush 80 in succession connects the slip ring 79 to contact segments D D D D D D. As a result the line is connected in sequence to the signaling levers of the three transmitters in th order:- dash lever of channel, dot lever of A channel, dash lever of 5 channel, dot lever of B channel,

' dash lover of C channel, dot lever of C channel and then th action is repeated in the same order. The connections made therefore are exactly the same as in the form of switch shown in Figures 9 and 10 allowing for three channels instead of two.

If all the signaling levers 7, 8, 9,- 1G, 73, 7a are on their back. contacts l1, l2, 13, 14, 75, 76 as shown in Figure 18, alternative positive and negative currents are sent to line, each being half the length of one aggregate signal as illustrated in Figure 15. Similarly, if one of the dash levers 8, 10 or 74 is on its front contact 16, 18 or 73, the first half signal becomes negative making a line signal 1G0 per cent negative and sending a dash in the respective channel as can be followed from Figure 15. Similarly, if one of the dot levers is on its front contact, the second half of the signal becomes positive, sending a signal to line which is 106 per cent positive.

The channel transmitters TA, TB, TC must in this case be driven at one third the speed of the aggregate signals and must be timed so that their contact levers are not moved between their stops during the time the lineis connected to them. The lines 81, 83 at the foot oi Figure 18 indicate the time intervals when the signaling levers oi the channels A, B and C respectively receive current impulses to give maximum tolerance for hunting of: the transmitters. Clearly the signal levers are operated by signals which are almost block signals showing only a small gap 84 between successive impulses.

The particular system of signalimpulses described in detail to a code in which the dots, dashes and spaces are represented in the particular manner already described, but clearly the automatic switches and the transmitter levers may be suitably connected to deal with any other arrangements of code signals. The signals may be divided among more than two or three channels as illustrated the drawings, and may even be divided among the channels unequally or irregularly in a predetermined manner by means of suitable switching arLangen'ients in order to increase the de 'ree of secrecy obtainable.

In order to separate the signals belonging to the two channels at the receiving station, a circuit arrangement may be employed in accordance with B1, sh. l-atent'llo. scarce granted to Imperial. & international Communications Limited and Harry Vernon i-Iiggitt dated December 24, 1931.

I claim:--

1. A telegraph. signaling apparatus for sending double-current cable'code signals of the type set forth, comprising a plurality of cable codetransmitters driven in synchroni '1. with the signals, means for sending on signals from said transmitters and synchronously-actuated switching gear organized to pass the from said transmitters to said sending-on n'ieans in the form of double-current cable code signals and to allocate the signals from the respective transmitters to separate channels in a predetermined sequence.

2. A telegraph signali g apparatus for sending double-c rrent cable code signals of the type set forth, comprising a plurality of cable code transmitters driven in synchronisin with the signals, means for sending on signals from said transmiters and consis of a telegraph line and synchronously-actuated switching gear organized to pass the signals from said transmitters to said line in the form of double-current cable code signals and to allocate the signals from the respective transmitters to separate channels in a predetermined sequence.

3. A telegraph si naling apparatus for sending double-current cable code signals of the type set forth comprising a pair of automatic cable code transmitters driven in synchronism with the signals but half a channel signal out of step with each other, means for sending on signals from said transmitters and synchronously-actuated switching gear organized to pass the signals from said transmitters to said sending-on means in the form of double-current cable code signals and to allocate the signals from the pair of transmitters to two separate channels in a predetermined sequence.

41. A telegraph. signaling apparatus for sending double-current cable ccde signals of the type set forth, comprising a plurality of transmitters each includin a pair of contact levers and arranged to produce cable code signals at said contact levers, said transmitters being actuated in synchronism with the signals, means for sending on signals from said transmitters and synchronouslyactuated switching gear organized to pass the signals from said transmitters to said sending-on means in the form of marking or spacing current impulses having a duration of a whole signal period and of marking and spacing current impulses in succession each having a duration of half of a signal period, said switching gear also being arranged to allocate the signals from the respective transmitters to separate channels in a predetermined sequence.

5. A telegraph signaling apparatus for sending double-current cable code signals of the type set forth, comprising a plurality of cable code transmitters driven in synchronism with the signals and each allotted to one channel, a combining switch furnished with the same number of effective contacts as there are channels and connected to the dot contact levers of said transmitters, a second combining switch also furnished with the same number of effective contacts as there are channels and connected to the dash levers of said transmitters, and synchronouslyactuated switching gear connected alternately to each of said combining switches so as to pass on the double-current signaling impulses.

6. A telegraph signaling apparatus for sending double-current cable code signals of the type set forth, comprising a plurality of cable code transmitters driven in synchronism with the signals and each allotted to one channel, a combining switch furnished with the number of eifective contacts as there are channels and connected to the dot contact levers or aid transmitters, a second combining switch also furnished with the same number of effective contacts as there are channels and connected to the dash levers of said transmitters, means for sending on signals from said transmitters and a reversing switch operated at the aggregate speed of the signals passed to said sending-on means and completing connections alternately to each of said combining switches so as to pass on the double-current signaling impulses.

7. A telegraph signaling apparatus for sending double-current cable code signals of the type set forth, comprising a plurality of cable code transmitters driven in synchronism with the signals and each allotted to one channel, a combining switch furnished with the same number of effective contacts as there are channels and connected to the dot contact levers of said transmitters, a second combining switch also furnished with the same number of effective contacts as there are channels and connected to the dash levers of said transmitters, means for sending on signals from "said transmitters and a reversing switch operated at the aggregate speed of the signals passed to said sending-on means and completing connections alternately to each of said combining switches so as to control at its contacts the current impulses passing to said sending-on means. 7

8. A telegraph signaling apparatus for sending double-current cable code signals of the type set forth, comprising a plurality of cable code transmitters driven in synchronism with the signals and each allottedto one channel, a combining switch furnished with the same number of effective contacts as there are channels and connected to the dot contact levers of said transmitters, a second combining switch also furnished with the same number of effective contacts as there are channels and connected to the dash levers of said transmitters, means for sending on signals from said transmitters, a reversing switch operated at the aggregate speed of the signals passed to said sending-on means and completing connections alternately to each of said combining switches and a relay with a split winding con nected to said reversing switch so as to pass double-current signal impulses to said sendingon means.

9. A telegraph signaling apparatus for sending double-current cable code signals of the type set forth, comprising a plurality of cable code transmitters actuated in synchronism with the signals and each allotted to one channel, means for sending-on signals from said transmitters and a rotary distributor switch for sweeping to said sending-on means the signal impulses from the contact levers of said transmitters, said distributor switch being furnished with a pair of contact segments for each channel, successive segments of each of said pairs being connected respectively to the dash and dot contact levers of the transmitter associated with the respective channel.

10. A telegraph signaling apparatus for sending doublecurrent cable code signals of the type set forth comprising a pair of signaling devices for producing respectively dot and dash cable code signals, means for sending on signals pr duced by said devices, and synchronously actuated switching gear connected to said signaling devices and to said sending on means, and organized to close contacts to connect said dot and dash signaling devices to said sending on means during alternate time intervals of the cable code signals respectively to cause the electrical condition of said sending on means to be determined by said dot and dash signaling devices during said alternate time intervals.

HARRY VERNON I-IIGGITT. 

